The present invention relates to a device and method for measuring the coefficient of performance of an installed heat pump having an auxiliary resistance heating capacity.
The definition of coefficient of performance (COP) for a heat pump in the heating mode is the ratio of the heat flow of the indoor unit to the power input to the heat pump. In order to calculate the COP of the heat pump, it is necessary to measure heat output, or heat flow, and electrical power input and ratio the two numbers to obtain a dimensionless number which is the coefficient of performance. The power input can be obtained by any of a variety of instruments, but heat flow is not easily or quickly measured, particularly on an installed heat pump.
In the prior art, there are several different methods of calculating the COP of a heat pump. These methods, however, either utilize equipment maintained in testing laboratories, or in the case of installed heat pumps, require extensive modifications to the heat pump and associated duct work and also involve considerable knowledge of a trained operator due to the calculations involved in obtainind the COP of a heat pump. These prior art methods, however, can result in significant errors in calculating the COP of an installed heat pump; accuracy of the heat flow measurement is generally directly proportional to the degree of instrumentation and to operator training. Thus, there is a need for a method and an instrument to carry out the method which performs repeatable laboratory-grade COP measurements on installed units which does not require operator calculations or elaborate measurement techniques.